Does ERG mode increase muscle fibre recruitment?

Had to jump on the trainer there for first time in 2 months. Did an easy Zwift workout as a warmup, then did a harder threshold/VO2 group workout straight after it, all in ERG mode.

Honestly, had to turn down the intensity on the last 10 mins. Legs really felt worked and fatigued. Had that jelly leg feeling a bit at the end too.

Thinking back over the past 6 to 8 months… only had maybe a dozen trainer rides max, and they all felt hard.

Got me thinking, maybe riding ERG mode should be kept up throughout the year, you know, maybe has other benefits you don’t get otherwise?

it’s definitely something you need to get used to (and therefore probably keep it up to date or loose it).
You have to keep your cadance up, if you don’t the resistance keeps fluctuating, and because it feels harder, you will probably try to pedal faster again until it drops, repeat…
Be as smooth and consistent as possible in your cadence to avoid this, but that puts another strain as outdoor riding.

But not sure if it’s beneficial for outdoor riding, maybe the most for TT, and the least for MTB, but for me just how indoor training with ERG works. I prefer the convenience of ERG and watching Netflix.
and I don’t think it’s bad for you to have continues strain during a workout.

ERG mode isn’t some magical thing. The “fatigue” you’re feeling is likely from the micro adjustments in power from variable cadence. It’s the same in resistance or sim mode if trying to hold constant power it’s just erg does it for you.

If anything erg makes you less fluid bc you think you’re better at holding power than you are

Hmm, if they went beyond “keep you honest” then the trainer vendor’s marketing machines would have been droning on and on about it for years and years. And I thought training included training the mind :thinking:

I use ERG for everything including the 180-200% sprint and hard starts. I find it keeps me committed to the interval and keeps me from easing off. Some theories say ERG training is bad because you don’t learn how to hold power, hasn’t been the case for me as I can hold my power very evenly because after 3 winters in ERG I’ve probably developed some kind of muscle memory.

Keeping a smooth cadence is key


I have moved away from erg mode a little bit recently (though I’m also typically now only on the trainer once, max twice a week). I found it was doing too much of the mental work for me, as well as not working brilliantly for transitions into/out of shorter intervals (but that is probably just the crapness of my Elite). I honestly think it’s just personal preference.


I doubt it. My only thought is that you might coast or soft pedal outdoors far more than you realize, and your rides are more variable than they are when on ERG mode where power is constant.

I’ve spent seasons on a non-smart trainer and on a smart trainer, I don’t think I’ve gained anything by using ERG mode. If I have it would be impossible for me to quantify in a real-world sense. It’s a very unrealistic way of putting out power, nothing is that smooth in real life except for a super consistent climb that you can settle into.

I like it, and I use it, but I’ve never thought that I should do ERG mode rides to maintain something.


Same. My pedal stroke is very smooth on both the flats and climbs, despite that Erg mode power is even smoother and feels downright unnatural.

Yeah, I spend my winters exclusively on the trainer and my impression when I go back outside is that the terrain sort of ‘lets up’ more frequently, even if it’s just for a second. I have an old road machine so I don’t even use erg, but being able to just pick a gear and pedal at your preferred cadence is still very different than the constant variations you get outdoors IMO.

Some other factors to consider (especially if you don’t ride indoors frequently) are the impact of cooling and potential differences in fit/position between the two circumstances.

1 Like

That depends. Holding 250W at 70rpm would recruit more type II (fast twitch, anaerobic, high force) fibers due to their high force producing capability. But, 250W at 100rpm more of the type I (slow twitch, aerobic, low force) muscle fibers would be used due to the reduce ‘force’ that is required. This is very noticeable in erg mode and that is why I used it exclusively on my trainer.

I always notice that when I do a slow spin my heart rate is lower than when I spin more quickly. So, if your goal is to build muscular strength, spin slow as you would when climbing. But, if your goal to improve endurance, spin quickly. At the end of the day, most of us select a cadence that utilizes a mixture of type I and II muscle fibers. Personally, I hover between 87-92 rpm.


My cadence has definitely suffered badly recently. I used to be at the upper end of average cadence. Even when I started road cycling I was doing rides 100 to 105 cadence, but I think looking back that was partly due to me doing the spin bike for a year before getting a road bike.

I’ve kept a high cadence for years until recently when I’ve upped my volume and rode outdoors almost exclusively (15 to 20 hour weeks). I’m climbing a lot and a lot of it at low cadence to keep myself in Z1 POL, but recently I feel it’s stressful to get into those higher cadences.

Last week when I was doing my POL intervals I was slogging them out at 75 to 85rpm. That’s really low for threshold and VO2 work, especially for me. Although quite impressed with my ability to now do that, seems my legs are stronger at this range and don’t tire as quickly, I knew I’d still burn out and it wasn’t sustainable when really doing longer efforts.

I’m wondering if this is related to the fatigue I was feeling today jumping back on the trainer and on ERG mode. The intervals weren’t as hard as what I was doing outdoor lately (4x8 etc) but I still dropped the power. Think it was called spaded sweetie that group workout.

As a side note - how long does it take to change muscle fibres from one type to another?

I wouldn’t over think this too much. Just ride and enjoy. But, if you are grinding (low cadence and high watts), I would shift to an easier gear to facilitate a quicker spin. Ideally, you want average between 90-100 rpm.

Personally, I would really struggle attempting threshold-VO2 workouts at a low cadence. It would not be sustainable as you pointed out too.

Muscle fibres can ‘shift’ over, but I do not know to what extent. I think this may have been answered in one of the podcasts. I would recommend searching in PUBMED at

Cheers and ride on!

I did a 1x35min at FTP today at 80rpm. My Allez is a 1x and the cog makes the 2t jump where I needed it, so it would have put me a little too high rpm wise for me.

I wouldn’t recommend going that low for that long, but it does leave a nice “pump” and make your legs look pretty jacked :rofl:

Ok, for starters, I have no science to back this post up. (And I don’t care.)

What I do have is 13 years on my indoor trainers, 5 in trainer road, so some historic data of progression.

I started out doing Spinervals DVD’s on my Kurt Kinetic trainer with Coach Troy (You can do it!). This was my introduction to actually practicing skills like cadence and form drills. It was great. Kept me almost fit.

After the Wahoo Kickr came a long, I wanted one but couldn’t justify the cost, but I discovered I could train with Virtual Power in Trainer Road by adding a speed and cadence sensor to my bike. $120.00 cost plus TR. Worked (and still works) great. I got into structured training, and learned a lot. Over 3 years my FTP rose to about 280.

Then I bought a used Kickr (now upgraded) and WOW it was different in ERG mode. I expected it would be harder. This was based on my previous data that clearly showed me fading on certain intervals during my programs. This fading is just how it is when you get tired as a weekend warrior. Sometimes I’d fade for a few seconds, sometimes I’d bonk the interval and just finish it low, but mostly I could not keep my sprint intervals on power.

So, I read a bunch about cycling theory to understand what I needed to change. The short version is: build your heart to pump more fully, build out your capillaries to move O2 to your muscles, then build out muscle power and speed.

(Read all of these fact sheets: EFR ~ Factsheets)

For the sake of this discussion, we’re talking about if ERG is better for building muscle power and speed. (Power = force (how hard you push) x speed (how fast you spin))

When I changed over to a Wahoo Kickr, I assumed that ERG mode would make me work hard for every full interval. No slacking off when I get tired. And yes, that’s what or does for me. I only like to train Low Volume (I do lots of outside winter activity) and it keeps me on target all the time. I feel that it helps me maximize my Low Volume training potential. It also allows me to focus on one aspect of generating power individually, or both together, or to focus on form.

My goal for the last 2 training season (Oct - May) have been to extend my FTP and increase my cadence. So, FTP endurance if that makes sense. I’ve seen my FTP test out now at 315 watts, but I don’t care about increasing it. It takes more work than I’m willing to put in. As a mountain bike instructor, I’ve found it more useful to be able to output 303w for 3 hours than 340w for 20mins. I’ve increased my usual cadence to 85 minimum with peaks over 120rpm. This gives me a lot of flexibility on how I generate watts when riding.

One counter intuitive thing I do is set my FTP slightly low in Trainer Road. I set it between 290 and 300 (not my tested 315). This keeps my target wattages in intervals a little lower than what I could peak at and I find it helps me to maintain and build higher cadences. It also means that I rarely bonk an interval. When I do want to work on slow cadence for climbing or standing, the slightly lower FTP saves my bad knees and hip for excess strain. I’m using ERG mode and I feel that I get good training results because I stay on power with high cadence in the complete interval even though the targets are touch reduced.

In Tour de Zwift this season consistently finished top 25% (top 10% a few times) in my categories, with output power over 300w for much of the ‘race’ ( note that I’m 100kg so there is no expectation of finishing first, but if the course of flat or rolling…)

I don’t think ERG has any real impact on muscle fiber develoment, other than the impact of getting you to work hard on target. But if you’re not completing the intervals and program with regular bonks, I’d suggest lowering your FTP to help you complete more.



I have had a big drop in cadence coinciding with starting with erg mode 3 years ago - I was a spinner always 95+ and now I’m down in the mid 70’s.

1 Like

What kind of workouts are you doing mostly on the trainer?

I am wondering what I’ve done ‘wrong’ recently to make such a noticeable change.

What trainer are you using?

Gearing in ERG?

How does that ERG gearing compare to your typical gearing use outside?

I’ve been off TR for the last two years but I do have a year of using TR with ERG mode to compare work out to work out with previous years on my dumb trainer. Post Wahoo purchase/ERG mode is 10+ RPMs lower than before I started using ERG mode

If I had to hazard a guess, my hunch is I probably had my FTP set too high when I switched over to ERG mode. ERG mode locked me in to targets whereas before I could subconsciously “fudge.” (Some view that as bad but the ability to back off slightly at will can really help with inaccurate FTP settings). After a season of essentially struggling, I basically trained myself to be a masher instead of a spinner now it’s hard to get my spin back up.

I still use ERG mode for steady-state efforts but I’m much more likely to switch it off for serious interval work. I find I’m both happier and train better if I’m in control of my power on hard efforts.

1 Like

Erg mode makes it easy to change the cadence - you have nothing else to do to adjust. So if you let yourself drop the cadence, you will get used to spin slower. On the other hand, if you increase the cadence, you’ll get used to spin faster…
In my case, I’ve always been a fast spinner (95-100rpm) - I have more cardio than force, so that suits me fine. I’ve been training with erg mode for a couple of years, and I still spin fast, and mostly faster on the road than on the trainer.

I do not want to start a new thread in case it has already been discussed and this thread seems relevant:
When in ERG mode and training longer intervals, many times if not perfectly rested and fueled I experience a progressive drop in my cadence that may eventually lead to a failed interval without maxing out heart rate and below my capacity outdoors.
It has nothing to do with staying on top of the cadence my legs just seem unable to keep up with the speed even if I really try to… needless to say I usually prefer to grind
Does someone know the reasons for this? Has anyone experienced something similar?